There is a continuing need in biomedical sciences for biocompatible compositions that can be used in manufacturing devices for implantation within or upon the body of an organism. Much of the focus in the past has concerned use of synthetic polymers. Many such polymers, however, suffer the drawbacks associated with their chemical and structural dissimilarities with natural materials. Fibrotic encapsulation, lack of cellular infiltration, and rejection are problems experienced by such implants. Efforts to overcome these issues have focused in part on use of biodegradable synthetic polymers as scaffolding to engineer prosthetic constructs to improve biocompatibility. Many such polymers, however, suffer the drawback of producing major degradation by-products that, in intimate contact with to individual cells, can produce an inflammatory response and decrease the pH in the cellular microenvironment. Thus, steps must be taken to ensure proper by-product removal from the tissue-engineered construct when using biodegradable materials. Another complication is that bioabsorbable structural materials are degraded over time, resulting in structural failure of the implant. Fibrotic encapsulation and lack of cellular infiltration also remain problems.
To overcome the drawbacks associated with synthetic implants, attention has turned toward use of collagen implants. Collagens are a family of proteins that are widely distributed throughout the body. This scaffolding material is one of the most prominent proteins present in animal tissue. Collagen is the principle structural element of most extracellular matrices and, as such, is a critical structural element of most tissues. There are several forms of collagen that exist in different types of tissue and organs.
To date, most efforts with collagen have focused on the use of collagen gels or solid collagen constructs such as films. A problem with these constructs is that they either lack structural strength (as with collagen gels) or lose strength after implantation. Harder collagen implants are broken down because their architecture and orientation differs from that of native tissues. Cells remodel implanted collagen to conform to the architecture and fiber orientation of normal extracellular matrices. This process causes structurally sound implants to lose integrity after implantation and ultimately to fail.
Thus, there exists a need in the art for collagen materials that may be used to form biocompatible implants that possess structural integrity and retain such integrity after implantation. Preferably, such materials should be able to mimic the chemistry and structure of extracellular matrices and promote infiltration of cells.